The present invention relates to ultrasonic transducers generally.
Various types of ultrasonic or acoustic transducers are known in the art. (It is noted that the terms ultrasonic transducer and acoustic transducer shall be used interchangeably herein throughout the specification and claims.) The following U.S. Patents are believed to represent the state of the art: U.S. Pat. No. 5,103,129 to Slayton et al., U.S. Pat. No. 5,094,108 to Kim et al., U.S. Pat. No. 5,054,470 to Fry et al., U.S. Pat. No. 4,959,674 to Khri-Yakub et al., U.S. Pat. No. 4,912,357 to Drews et al., U.S. Pat. No. 4,888,516 to Daeges et al., U.S. Pat. No. 4,869,278 to Bran, U.S. Pat. No. 4,825,116 to Ito et al., U.S. Pat. No. 4,659,956 to Trzaskos et al., U.S. Pat. No. 4,528,853 to Lerch et al., and U.S. Pat. No. 4,208,661 to Vokurka.
Acoustic transducers are characterized inter alia by an angle of dispersion, and the ability to vary this angle is of major concern in transducer design. There are three major approaches in the prior art to vary the angle of dispersion:
1. Modification of transducer frequency
2. Modification of transducer size
3. Use of a horn to limit the angle of dispersion
Each of these approaches has its advantages and disadvantages, and the transducer designer generally selects a solution which best fits his/her requirements,
The present invention seeks to provide an improved ultrasonic transducer which provides a compact and inexpensive solution to the problem of varying the angle of dispersion.
The present invention provides an ultrasonic transducer in off-axis relationship with a reflective surface, which surface is preferably paraboloidal. The ultrasonic transducer directs a beam onto the reflective surface, which beam is reflected therefrom to the outside world. If the beam is reflected from an object in the outside world back to the reflective surface, the reflective surface focuses the returned ultrasonic energy onto the transducer, thereby causing the transducer to provide a signal output in accordance with the reflected energy. A stray energy shield is mounted on the ultrasonic transducer for limiting the angular range of ultrasonic energy which impinges on the transducer.
It is noted that U.S. Pat. No. 3,792,480 to Graham and U.S. Pat. No. 4,791,430 to Mills both describe ultrasonic antennas with the source of ultrasonic energy off-axis to the reflective surface. However, both of these references are not concerned with transducers and indeed the structures shown in both of these references are not readily applicable for reflecting ultrasonic energy from the reflective surface back to a transducer for providing a signal output, as is of course essential in ultrasonic transducer design. It is the present invention which provides a novel arrangement of off-axis transducer and stray energy shield in order to achieve a compact and inexpensive transducer design with remarkably accurate and reliable performance. This novel arrangement is not taught nor suggested by any of the above cited art.
There is thus provided in accordance with a preferred embodiment of the present invention an ultrasonic transmitting and receiving transducer reflector assembly including an ultrasonic transducer support and a reflector extending therefrom, the reflector defining a reflective surface having optical power, an ultrasonic transducer producing a beam which is directed onto the reflective surface and providing a signal output from ultrasonic energy reflected thereonto from the reflective surface, the transducer being mounted on a mounting surface of the support in off-axis relationship with the reflective surface, and a stray energy shield at least partially enveloping the ultrasonic transducer for limiting the angular range of ultrasonic energy which impinges on the ultrasonic transducer.
In accordance with a preferred embodiment of the present invention the ultrasonic transducer support and the reflector are integrally formed as one piece. Alternatively the ultrasonic transducer support, the reflector and the stray energy shield are together integrally formed as one piece. As another alternative, the ultrasonic transducer support, the reflector and the stray energy shield are together integrally formed as one piece with a housing of the transducer.
Further in accordance with a preferred embodiment of the present invention the ultrasonic transducer is selectably locatable within the stray energy shield.
Still further in accordance with a preferred embodiment of the present invention a distance of the ultrasonic transducer relative to the reflective surface determines a shape of a beam emanating from the transducer and reflected by the reflective surface.
In accordance with a preferred embodiment of the present invention the ultrasonic transducer is located at a focus of the reflecting surface. Alternatively the ultrasonic transducer may be located inwardly or outwardly of a focus of the reflecting surface.
Further in accordance with a preferred embodiment of the present invention the ultrasonic transducer is threadably mounted within the stray energy shield.
In accordance with a preferred embodiment of the present invention the reflecting surface is a paraboloid.
Additionally in accordance with a preferred embodiment of the present invention the ultrasonic transducer and the stray energy shield are pivotally connected to the support, such that an angle of incidence of a beam reflected from the reflecting surface with respect to the transducer is variable.
There is also provided in accordance with a preferred embodiment of the invention an integral ultrasonic transmitting and receiving transducer assembly comprising an ultrasonic transducer producing a beam and a multiple beam path horn assembly operatively associated with said ultrasonic transducer and directing said beam along at least two distinct paths.
In accordance with one embodiment of the present invention, the two distinct paths are at least partially overlapping. Alternatively, the two distinct paths are not overlapping.